PPA Subtyping: Helping or Hindering the Understanding of PPA?

Decoding and understanding problem

Partners in FTD Care, Fall 2020
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by Emily Rogalski, PhD

One of the most confusing topics for PPA caregivers, clinicians, and researchers studying the condition has been the nomenclature associated with it. PPA subtyping—delineated as agrammatic, semantic, and logopenic subtypes—vary in clinical features and tend to have different patterns of brain atrophy, as well as different probabilistic relationships with underlying pathology. These subtypes were developed for research purposes, and were thus incompletely validated before making their way into clinical discussions.

On the positive side, subtyping gives families a shorthand way to describe the constellation of
symptoms a person with PPA is experiencing. But admittedly, there are challenges with the current diagnostic system. Research suggests that up to 30% of individuals with PPA do not meet criteria for any of the three subtypes at the time of diagnosis. Since PPA is progressive—meaning symptoms get worse and change over time—it can also be difficult to subtype later in the disease course. And practitioners with limited specialist experience in PPA can find it difficult to diagnose the condition itself, let alone discern a subtype.

Is there an alternative to subtyping? What if a person with PPA does not meet criteria for a subtype? Neuropsychologists and speech-language pathologists with PPA expertise can provide detailed assessments of the challenges and relative strengths that the individual is experiencing. This information establishes expectations for which everyday activities may or may not be challenging for those with PPA, and can also contribute to an individualized care plan.

PPA has gotten more attention in the scientific literature in recent decades, with substantial progress being made in our understanding of the syndrome and the connections between its symptomatology, progression, pathology, and genetic implications. But many hurdles remain, particularly in terms of ensuring that people with PPA and their care partners and caregivers receive optimal information and support at diagnosis, as well as appropriate treatments, interventions and/or management strategies throughout their PPA journey.

Despite the murkiness of PPA subtyping, clinical researchers have found value in such nomenclature. But for families living with PPA, value lies not in overeducating them about their PPA subtype, but rather in anticipating their needs and equipping them with the support and information necessary to ensure the best quality of life for the road ahead. Such supports include educating them about optimizing communication to ensure the best quality of life, the role of dynamic clinical decision making in the face of declining language and other cognitive and behavioral functions, as well as emerging treatment and/or research options.

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